The present disclosure relates to a method and apparatus for testing materials. More particularly, but not exclusively, this invention concerns a method and apparatus for testing materials using infrared spectrometry. The invention also concerns the calibration of an infrared spectrometer for use in testing materials using infrared spectrometry.
Infrared spectrometry may be used to measure and/or monitor physical properties of composite materials, such as advanced polymer matrix composites with high strength fibers. Composite materials are used extensively in the aerospace industry. The aerospace industry has exacting standards relating to materials quality. During the lifetime of an aircraft, various events may occur which can damage part of the aircraft. Example of events include lightning strikes, holes being drilled in the aircraft during manufacturing or maintenance procedures, electrical arching, and laser treatment of materials during manufacturing or maintenance procedures. These events may result in the thermal degradation of composite materials making up the aircraft. Alternatively, during the manufacture or maintenance of an aircraft or aircraft component, a composite material may be overheated, for example during the curing of a composite material.
European patent publication number EP 2138829 discloses measuring the thermal effect of composite materials used in the aerospace industry using mid-range infrared spectroscopy. A hand-held infrared spectrometer is used to take measurements of a material, with the infrared spectra compared to a database of spectra to determine a physical property of that material. The hand-held infrared spectrometer is calibrated using a multivariate calibration process. Such a process can be time consuming.